The goal of this research is to provide basic information about the role of water in cellular function. Achievement of the goal depends first on determining the physical properties of water in living tissues and second, determining the changes in the physical properties of tissue water associated with changes in physiological state. Spin-echo techniques will be used to determine precise physical parameters (relaxation times and diffusion coefficient) of water in rat muscle existing in different physiological states. These physical parameters reflect the state of the water molecules in the cellular environment and are known to change with alterations of the functional state of the muscle tissue, such as normal postnatal development and contraction. Other manipulation of the tissue, such as dehydration and temperature variation will also be used to induce changes in the physical parameters of cellular water. The information resulting from these studies will provide insight into the physical state of cellular water permitting the construction, testing, and refinement of models. Simple mathematical models describing the behavior of water in living cells have been developed and will be extended. The equipment for our project will be made available to other scientists in the community. Approved projects include studies of the physical properties of water in collagen-water systems, cardiac tissues, skeletal muscle in diseased states, red and white blood cells, subcellular particles, kidney tissues and neoplastic tissue.